This invention relates to a self-aligning ring joint for joining concrete pipes of the type employing sealing rings made of a resilient and flexible material, and more particularly, to in improved sealing ring which when used with concrete pipes that have ends of a special configuration, will serve to maintain the ring joint in a central position between two adjacent pipe ends.
Conventional ring joints employing sealing rings generally comprise a ring made of cast iron or the like and a sealing ring provided internally at each end thereof, said sealing ring including a main ring having an inside diameter approximately equal to the outside diameter of a pipe end and an integral lip ring, or mouth, depending therefrom having an inside diameter substantially smaller than the outside diameter of the pipe end so that when a pipe end is pushed into one end of the ring joint the mouth of the sealing ring will expand and stretch around the pipe end, forming a watertight seal.
One major defect of such ring joints is that there is no way of accurately aligning the ring joint so that the open ends of each pipe are positioned at the exact center of the ring joint. Due to this fact, the amount of pressure on each sealing ring will not be equal. Another inherent defect of such ring joints is that as the mouth of the sealing ring is stretched over the end of the pipe with no external pressure to offset the effects of this outward expansion, the sealing ring will lose its flexibility and resilience, causing it to stretch or crack, whereby it resistance to high pressure within the joint is greatly decreased, greatly increasing the chances of leakage. Due to the same reason, ie. lack of external pressure, or prestress, to the sealing ring, any shifting of the pipe is likely to break the watertight seal.
It is a purpose of the present invention, therefor, to eliminate or improve the above said defects and to provide an improved ring joint capable of aligning itself so that two pipe ends joined thereby will always be positioned centrally of the ring joint so as to equalize liquid pressure acting on each of the sealing rings.
It is a further purpose of the present invention to provide such a ring joint having improved sealing rings which enable the ring joint to maintain proper alignment between the pipe sections joined thereby.
It is yet a further purpose of the present invention to provide a sealing ring for such a ring joint which under deformation is capable of being compressed between said ring joint and the pipe ends joined thereby to insure a watertight seal, of enabling the ring joint to align itself properly, of enabling the ring joint to accommodate shifting of the pipes, and to generally increase the useful life of the ring joint.
It is another purpose of the present invention to provide a special type of end for pipes to be joined in the manner to be described so that the force applied to the sealing rings thereby enables proper alignment of the ring joint.
It is yet another purpose of the present invention to provide a durable seal even after ageing has caused the material of the sealing rings to loose its elasticity.